Move ThreadableLoaderClientWrapper to Oilpan heap

As preparation for moving ThreadableLoader to Oilpan heap, this CL moves
ThreadableLoaderClientWrapper to Oilpan heap.

This CL also removes ThreadableLoaderClientWrapper::ResourceTimingClient and makes
ThreadableLoaderClient::didReceiveResourceTiming() to be called also for
ThreadableLoaderClient associated with WorkerThreadableLoader.

BUG=587663

Review-Url: https://codereview.chromium.org/2146333002
Cr-Commit-Position: refs/heads/master@{#407058}
4 files changed